Background Patients with small ventricular septal defects (VSDs) are thought to have excellent long-term survival, although complications may not be uncommon. Methods We identified all patients aged ≥ 16 years with native isolated VSD between January 2000 and September 2013. Clinical outcomes were retrospectively reviewed. Transthoracic echocardiograms performed within 2 years of last assessment were reviewed for hemodynamic sequelae. Results Two-hundred-and-thirty-one patients, 100 (43%) male, mean age at last follow-up 34 ± 13 years were studied. During the recorded period there were no deaths. The majority (224/231; 97%) were asymptomatic. Documented arrhythmias occurred in 7 patients (3%), double-chamber right ventricle (DCRV) in 29 (13%), more than mild aortic regurgitation in 6 (3%) and infective endocarditis in 24 (10%) patients. Surgery due to complications associated with VSD was performed in 26 (11%) patients at a median age of 27.6 years (IQR: 16.1–38.7) due to DCRV (n = 17, 65%), infective endocarditis (n = 6, 23%), progression of left–right shunt (n = 2, 8%) and aortic regurgitation (n = 1, 4%). At most recent echocardiography (n = 164), 10 (6%), had reduced LVEF, 34 (21%) had increased LVEDD and 17 (10%) had LVESD > 4.0 cm. Thirty-two patients (25%) with normal LV dimensions had LA enlargement suggesting LV diastolic dysfunction. Conclusions We report a non-negligible incidence of major complications or clinical events during late follow-up of adult patients with restrictive VSDs. Furthermore, we show co-existing LV dysfunction, systolic or diastolic in a subset of patients. Indication for VSD closure in childhood may be recognized, whereas lifelong follow-up for adult with restrictive VSDs is clearly warranted.